Light emitting elements in the form of LEDs are widely used in display screens, particularly for large scale applications. Larger scale applications include advertising screens, information screens, such as those in building lobbies, airports, train stations and the like and for entertainment purposes, such as those used at concerts and in television studios.
With reference to FIG. 1A, to achieve the large display areas typically required for such applications, one type of large LED display screen 2 comprises a plurality of smaller display modules 4a, 4b which are coupled together. Such modules must be physically held together in the desired formation to form the finished screen. The modules must also be coupled together for both power and data transmission through all of the modules to power the LEDs 6 of each module and to cause the array of LEDs on each module to display the respective portion of the overall images being displayed.
Larger scale LED display screens are producing higher resolution images by reducing the LED pitch size, i.e. by reducing the distance between the centres of adjacent LEDs and hence increasing the number of LEDs per unit area. As the pitch size decreases, it is increasingly important to accurately align adjacent display modules. Misalignment of modules results in distorted images being displayed and thus the image quality is impaired. Improving or even maintaining image quality in the presence of decreasing LED pitch size, but in the absence of an accurate means of joining the modules therefore becomes more difficult.
Many applications require LED display screens to conform to one or more curved surfaces. With reference to FIG. 1B, when the screen 2 is bent to conform to a curved surface, display module 4a is at an angle to display module 4b, such that the pitch size between adjacent modules is different to the pitch size for each module, which leads to distorted images. A gap 8 is also created between adjacent modules, which is unsightly and produces a display screen with poor aesthetics. Existing display module coupling systems cannot maintain the LED pitch size between adjacent modules.
Some display screens are flexible, which is achieved by using suitable materials that enable the individual display modules forming the screen to bend. However, bending the display modules changes the pitch size between adjacent modules resulting in distorted images being displayed. The problem is exacerbated with increasing curvature of the modules.
Some known methods of coupling LED display modules for flexible large scale displays comprise interlocking ridge and lip arrangements. However, these do not maintain the pitch size between adjacent modules. At least some of these also have the drawback that access to the modules from the front of the module, for example for maintenance or test purposes, is not possible. Therefore, access must be via the rear of the module. Since the displays are often mounted to a curved surface, access from the rear can also be difficult, if not impossible. Therefore, in some cases, the displays must be dismantled and/or removed from their mounting to permit access.
Another problem with conventional flexible displays is that the power and logical connections at the rear of the multiple modules can be cluttered, which can be time consuming to disconnect and diagnose problems during maintenance. This problem is exacerbated with the size of the display and the increasing numbers of modules.
Where large scale LED displays are used in external environments, another requirement is that the LED screens and their components need to be waterproof.